1. Field of the Invention
The present invention relates to a movable coil driving unit, and particularly to a movable coil driving unit having a moving coil with improved driving responsibility and reduced power consumption.
2. Description of the Prior Art
Movable coil driving units are widely used for speakers, mechanisms for driving the heads of magnetic disk units, etc. Recently, they are also used for linear motors. The linear motor is based on the Fleming's left-hand rule to use force generated when electrical current is applied to a coil positioned in a magnetic field. If a permanent magnet which is a supplying source of magnetic flux is fixed, the coil is moved by applying currents to the coil, while, if the coil is fixed, the permanent magnet is moved. The former case constitutes a movable coil driving unit, and the latter a magnet driving unit.
The magnet driving unit is not applicable for a mechanism which needs a high-speed response, because the weight of the permanent magnet is too heavy to be a driven member with a high-speed response. On the other hand, the movable coil driving unit is widely applicable for devices such as speakers and mechanisms for driving the heads of magnetic disk units which require the high-speed responsibility, because a coil and a non-magnetic coil bobbin of the movable coil driving unit are sufficiently light as moving members to realize the high-speed response.
According to a conventional movable coil driving unit, a moving coil of the driving unit is connected to a power source fixed to an external fixed member from which the coil receives current through coil leads extending from the ends of the coil in a manner that the coil is suspended by the coil leads.
In such a conventional movable coil driving unit, the coil leads for suspending the coil will cause resistance against the movement of the coil as well as bothering the range of coil movement. To reduce the resistance against the coil movement, the diameter of the coil leads shall be reduced. However, if the diameter is reduced, an electrical resistance value of the coil leads is increased so that power consumption also is increased. Further, if the number of windings and the length of the coil are increased to raise the driving force of the coil, an electrical resistance value of the coil is increased to increase power consumption also.
In addition, if the diameter of the coil leads is enlarged to reduce the power consumption, mechanical resistance of the coil leads is increased to deteriorate a response in driving the coil. Therefore, there is a requirement to provide a movable coil driving unit which has a good response in driving a coil while realizing low power consumption.